Conventionally, photo image embroidering has been performed in which embroidery is produced based on photos taken by digital cameras or film cameras. Photo image embroidery uses sources such as image data taken by digital cameras, and scanned images of film. Based on such image data, segment data indicating shapes of stitches and thread color data indicating the color of stitches are generated to provide an embroidery data carrying color-by-color information of stitches.
Such embroidery data is generated by an embroidery data generating apparatus, one example of which is suggested in JP 2001-259268 A (hereinafter referred to as reference 1). In the disclosed embroidery data generating apparatus, in order to approximate the resulting embroidery to the original photo image, stitches are formed in various orientations fully spanning 360 degrees instead of being limited to a single orientation.
More specifically, for each pixel constituting the image data, orientation of stitch (angular feature) located on a given pixel and its magnitude (feature magnitude)are calculated for generating the segment data. The angular feature and its magnitude are calculated based on the luminance of the pixels surrounding the focus pixel where focus is currently being placed by the system and magnitude of angular feature increases as difference in luminance relative to the surrounding pixels increase.
When generating embroidery data, sewing sequence is determined as follows. First, among the segments sewn by the same thread color as the initially sewn segment, the segment located in the closest proximity of the initially sewn segment is searched and identified as the subsequently sewn segment. Likewise, among the segments sewn by the same thread color as the subsequently sewn segment, the closest segment is searched and identified as the next segment. A running stitch is formed from a start point to an end point of a segment, whereas a jump stitch is formed from the end point of the current stitch to the start point of the subsequent segment. The above described procedure is repeated for each thread color to generate the embroidery data.
Jumping stitch requires the jump thread to be removed after it has been sewn. Further, while the jumping stitch is being formed, reverse stitch needs to be formed to prevent the thread from coming out of the location where the jump stitch is subsequently cut. Stated differently, jump stitch requires cumbersome task when it is being sewn and after it has been sewn.
In order to minimize jump stitches, embroidery data with jump stitches converted into running stitches are generated when predetermined conditions are met. The first of the two predetermined conditions is that a running stitch is sewn over the jump stitch with another thread. In such case, since the jump stitch is covered by another thread, converting the jump stitch into a running stitch will not be a problem. The second of the two predetermined conditions is that when a thread needs to be sewn underneath the jump stitch, the difference between color of the thread sewn underneath and the thread color of the jump stitch needs to be equal to or below a predetermined similarity threshold. If the color of thread sewn underneath and the color of threads in its periphery have little difference, converting the jump stitch into a running stitch will not render the running stitch conspicuous.
However, even if the difference between the color of the thread sewn underneath and the thread color of the jump stitch is at or below the similarity threshold to meet the second predetermined condition, the direction of the stitch may render the running stitch conspicuous even if it does not stand out in terms of thread color. One such example is shown in FIG. 26 of the present exemplary embodiment. As can be seen in area 900 of FIG. 26, when stitches inclined by approximately 90 degrees are formed continuously in an area where most of the stitches are inclined by substantially 0 degrees, the series of continuous stitches, being directed in a different orientation from the rest of the stitches naturally stand out. Stated differently, when stitch/stitches being considerably inclined relative to the underlying stitches are formed in a substantial length, it/they may impair the look of the outcome of the sewing operation.